In the most commonly used blade feed concept of the prior art the blades are fed with cooling air via rotor bores (see for example document WO 2010108879 A1). The increase of the pressure is done via pumping work/centrifugal forces. This is the most common blade feeding system for internal cooled rotating gas turbine blades. This solution might cause life time problems. If not enough space is available, the needed pressure rise might not be sufficient.
Several other blade-feeding concepts exist:
Object of document GB 2225063 is a turbine comprising a stator and a rotor and means for supplying cooling air from the stator to rotor blades secured on the rotor, wherein on the rotor the air supply means includes an insert fitted between each blade base and the rotor disc and forming a deflection chamber closed towards the low pressure side of the rotor, while on the high pressure side the or each insert projects radially inwardly towards the hub over the rotor disc edge so as to form an annular air inlet aperture of the deflection chamber, and on the stator the air. Supply means includes an annular air outlet nozzle directed generally radially outwardly towards the air inlet aperture.
Document U.S. Pat. No. 5,984,636 A describes a cooling arrangement for a bladed rotor in a gas turbine engine, wherein each of the blades includes cooling air passages and a cover with curved fins is mounted adjacent to but connected to the rotor and spaced apart slightly from the rotor disc to form a passageway for the cooling fluid. The cooling arrangement includes a tapered, conically shaped inlet formed in the cooling passage which then diverges to form a diffuser near the outer end of the passageway. The cover includes an enlarged inner portion and a thin outer wall portion beyond the free ring diameter. A hammerhead is formed at the outer periphery of the cover whereby the hammerhead will move closer to the disc in response to centrifugal forces, thus sealing the passage.
Feeding the blade via rotating cover plates (e.g. U.S. Pat. No. 5,984,636). The cover plates are mounted adjacent to the rotor. They are fed on a relatively low radius and the pressure rise is achieved with vanes working like a radial compressor. Complicated design making a separate part attached to the rotor necessary.
Document U.S. Pat. No. 4,178,129 A discloses a cooling system for a turbine of a gas turbine engine, said system comprising a turbine rotor with blades extending there from: a plurality of circumferentially closely spaced pre-swirl nozzles defining a substantially continuous annular outlet flow area through which flows, in operation, a cooling fluid; and a plurality of circumferentially spaced pitot receivers projecting from the blades of the turbine in a direction towards the pre-swirl nozzles and terminating at their free open inlet ends in closely spaced relation to the nozzles with the ends being substantially perpendicular to the relative approach vector of the fluid from the nozzles, the pitot receivers being sized and positioned to collect a portion only of the pre-swirled cooling fluid from the nozzles and to direct it to a portion only of the interior of each of the blades of the turbine.
Thus, recovering pressure from total relative pressure is done in both the pitot tubes and the shank cavity feed. Disadvantageously, the pitot tubes are emerging in to the supply cavity.
Document U.S. Pat. No. 4,348,157 A teaches an air cooled turbine which has cooling air provided through pre-swirl nozzles into an annulus formed between radially inner and outer seals and then into cooling air inlets to the turbine blading, has leakage air deflector means to prevent the leakage flow from the inner to outer seal interfering with the cooling air flow. The deflector means may comprise leakage flow inlets adjacent the inner seal, channels extending radially and cooperating with the turbine rotor to provide passages for the leakage flow to a location radially outboard of the cooling air inlets to the turbine blading, and open portions through which the cooling air can flow to the cooling air inlets. The channel outlets of the deflector may be arranged so that some of the leakage flow can be directed to cool a less critical part of the turbine blading the remaining leakage flow being directed radially outboard of the cooling air inlets to a more critical part of the turbine blading which are arranged to receive the normal cooling air flow.
Document WO 03036048 A1 describes a turbine blade for use in a gas turbine engine, the engine having a hot gas path, a cooling air plenum, and a single stage high work high pressure turbine, the turbine disposed in the hot gas path and having a rotor and a turbine direction of rotation about an axis, the turbine blade comprising: a root portion adapted for mounting to a rotor; an airfoil portion extending from the root portion; a cooling air inlet duct adapted to communicate with the cooling air plenum when installed to the rotor, the air inlet duct having an inlet scoop adapted to extend into the cooling air plenum, the inlet scoop having an inlet scoop aperture oriented and adapted to capture cooling air from the cooling air plenum as a consequence of turbine rotation when the blade is mounted to the rotor; and a cooling air channel defined in an airfoil portion of the blade, the cooling air channel communicating with the cooling air inlet duct and the hot gas path of the engine, the cooling air channel being adapted to permit cooling air captured from the plenum by the cooling air inlet duct to pass through the channel to air outlet means for the purpose of cooling the blade.
The transfer of cooling air from the stationary frame of reference to the turbine blade root in the rotating frame of reference is still afflicted with problems and should be improved in order to improve the efficiency of the turbine.